For me the whole concept of docking ring was always weird and I take it merely as ingame representation of landing ability. I mean I understand the concept of mooring point - the ship moor there and cargo is delivered by space elevator from the ground. It saves lot of fuel which larger ships would have to burn during take off from the ground, not to mention that really large ships are physically unable to make re-enter into atmosphere without risking serious hull damage due to forces which are pushing onto them - they could probably survive it due to advanced materials, but doing it on regular basis is not realistic.
But the docking ring? What is the point of bulding massive structure and forcing the snubs and freighters to fly through it? It can´t prevent any planetary attack anyway, because attacking forces can simply enter the planet´s atmosphere anywhere else.
